Modulator



May 14, 1940.

AMPLIFIER e. 1. USSELMAN MODULATOR Original Filed m. 29, 1936 Y AMPL.

INVENTOR G.L. U SELMAN ATTORNEY Patented 2.201.017; MODULATOR George 'Lindley Usselmam'Port Jefferson, N. 2.,

, asslgnor' to Radio Corporation of America, a

corporation of Delaware r Application January-29, 1936, Serial No. 61,259,

now Patent No.'2,134,065, dated October 25,

V 1938, which is a division of application Serial No. 524,247, March 21,- 1931, now Patent No.

2,0 7d,449, dated March 28, 1937.

Divided and this application March .10, 1938, Serial No.

w en

4 Claims. (or. 179-1715) invention relates to modulators and especially to sideband modulators of the electron discharge device type. This application is a division of my United States application #61359 5 filed January 29, 1936, now Patent #2,134,065, dated October 25, 1938, the said application being in turn a division of my United States aplication #52d2d'l filed March 21, 1931, now Patent #hmdddildated March 23, 1937. 1 In order to produce sideband energy from carrier energy and energy of a frequency other iifl. the carrier energy while at the same time suppressing the carrier energy, it has been proposed to apply carrier energy to the grids of a pair of triodes cophasally and the other energy,

usually modulating energ to the same grids in phase opposition. By virtue of the fact that the two sources of energy were coupled to the same electrodes, undesired interaction between them I frequently took place.

It E an object ofthis invention to provide a carrier suppression modulator wherein such in teraction is edectively prevented. ,Briefiy, to do so,'according to my present invention, I'use four element or screen) grid tubes, or in other words,

tubes having more than three electrodes for electron discharge devices, to like pairs of grids of.

which I apply eitherthe modulating or carrier energy in phase opposition and to the other grids' .10. I apply the carrier or modulating energy cophasally. In this manner the energy sources are kept separate and prevented i'rom interacting upon one another.

Sometimes it is desirable that a small amount of carrier energy be transmitted in addition to the sideband energy. Accordingly, a further object of the present invention isto provide an arrangement of electrondischarge devices wherein carrier energy is only partially suppressed. 40 More specifically, and one way of doing so,v according to the present invention, the'grids of screen grid tubes are polarized diilerently and carrieralternatingenergysuppliedthereto. Other grids oi'the system are supplied with modulating energy. As a consequence, in the output circuit. of the tube arrangement, sideband energy and a certain? amount of carrier energy will appear.

Other general objects of my present invention are to provide transmitting and receiving systems utilizing my improved sideband or carrier suppresslon modulator.

While I have sought to define my invention in its broadest aspects in the appended claims. it may best be understood, however, both as to its structural ortion and mode of operation .order of magnitude in frequency relative to by referring to the accompanying drawing, wherein thesingle figure illustrates 'a carrier suppres sion system, according. to the present invention, wherein the carrier is not totally but only partially suppressed. I Referring to the accompanying drawing, relatlvely low frequency modulating energy, which may be considered energy oi one order of magnitude in frequency, from a suitable amplifier 2 connected with source I is applied in phase op- 10 position through the medium of transformer 4 to'the'screen grids l2 adjacent the anodes ll of electron discharge devices ill, of the screen grid type; To the control grids 6 or the grids adjac'ent to the cathodes 8 of tubes id, there is apl8 plied cophasally through condensers W, 50 from a suitable source 20, carrier potentials or energy which may be considered energy of a different energy from source 2. h

By virtue of the application to the grids of electron discharge devices lb of energy of diii'erent frequencies, there will appesr'in the output circult 62 coupled 'tothe devices, energy of frequencies equal to the sum and difference of the I 'irequencies from sources 2 and 2d.

The signal modulating energy is applied to the grids II, as shown, which are those adjacent the anodes of devicesv ill. The grids] of tubes ill are paralleled for high frequency currents by con- Q denser 50 and are biased or. polarized different amounts by source Cl and reactances 12 connected as shown between the grids and by a further reactance I3 to the negative terminal of a source of potential. To prevent the flow of a high frequency currents from source 20 in direct current source 68, chokes I2 are inserted in series with the biasing connections. As indicated above, the values of III and I0 aresuch that the high frequency energy from III is applied sub- 0 stantially in. phase to the grids I. As an addiodes of tubes III are polarized differently, a certain amount of carrier energy will always appear 'in the output circuit 82 of screen grids Ill. The

carrier energy and the sideband energy may than go be amplified by suitable amplifier it and radiated by means of a suitable antenna 8i.

Of course, by including in amplifier 64, suitable filters, the carrier energy and one or the other sldebands may be transmitted as desired rather than transmitting both sidebands and the carrier.

It is obvious that various minor changes will readily suggest themselves to those skilled in the art. Consequently, my invention is not to be limited to the modifications described, but solely by the scope of the claims which I have appended hereto.

I claim:

1. In a carrier suppression modulator a pair of electron discharge devices each having a cathode, an anode, a grid adjacent the cathode and a grid adjacent the anode, means for applying cophasally to the grids adjacent the cathodes relatively high frequency energy, a source of modulating potentials, a balanced push-pull circuit for applying modulating potentials from said source in phase opposition to the grids adjacent the anodes of said tubes, and means connected with the grids adjacent the cathodes and said cathodes for biasing said grids to different direct current potentials relative to said cathodes.

2. In a system for transferring intelligence from one geographically situated point to another by propagated electro-magnetic wave energy derived from the flow of high frequency undulatory electrical currents operated upon in accordance with the intelligence to be transmitted, the combination of a pair of electron discharge devices each having a cathode, an anode, a grid adjacent the cathode and a grid adjacent the anode, means for subjecting the grids'adjacent the cathodes of I said devices to uni-directional potentials of different values, means for subjecting the same grids to undulatory carrier potentials substantially cophasally, and balanced circuit means for subjecting the grids of said devices adjacent said anodes to potentials of another order of frequency and in phase opposition.

3. In a balanced modulator for modulating the electrical waves derived from a source of undulatory energy by means'of signalling waves of another frequency and for preventing reaction between said -waves other than said modulating reaction and for controlling the amount of energy of a frequency equal to the frequency of the waves to be modulated in the energy resulting from the modulation, a pair of electron discharge devlces,

each having'a cathode, a control electrode, an anode, and an auxiliary electrode, a circuit for applying positive potentials to said auxiliary elec-' trodes, means for applying signalling current potentials in phase opposition to said auxiliary electrodes in said devices, a circuit for applying diflerent values of direct current potential to the control electrodes of said devices to control ,of one pair of like grid-like electrodes in said devices relative to the cathodes of said devices, a source of carrier wave oscillations, circuits connecting said source of carrier wave oscillations to said same pair of like grid-like electrodes to apply thereto carrier waves in phase, means reactive at the frequency of said oscillations in said direct current circuits, a second source of oscillations of different frequency, and a balanced push-pull circuit coupled on the one hand to said second source of oscillations and on the other hand to another pair of like grid-like electrodes in said devices to apply thereto oscillations of said different frequency in phase opposition.

GEORGE LINDLEY USSELMAN. 

